Page 18 - The Biochemistry of Inorganic Polyphosphates

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Introduction
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The discovery by R. Reusch (Reusch and Sadoff, 1988; Reusch, 1992; Reusch, 2000),
which proved the involvement of PolyPs in the formation of channels across the cell mem-
branes, extended our previous notions of the function of these compounds. Such channels
formed by PolyPs and poly-β-hydroxybutyrate with Ca 2+ are involved in the transport
processes in organisms from different evolution stages.
Surely, the most important function of PolyPs in microorganisms – prokaryotes and
the lower eukaryotes, which depend a lot on the changing environmental conditions –
is phosphate and energy reservation. In this connection, under certain growth conditions
these organisms are able to accumulate PolyPs in much greater amounts than the higher
eukaryotes, the dependence of which on external factors is much less due to homeostasis,
being strictly regulated by hormones.
The important achievement of recent years has become the finding of non-identical sets
of enzymes of PolyP metabolism in different organelles of eukaryotic cells, obtained mainly
for yeast (Kulaev and Kulakovskaya, 2000; Lichko et al., 2003a). This result is in favour
of considerable distinctions in the physiological role of PolyPs in different compartments
of eukaryotic cells.
One of the basic questions, which has only just begun to be investigated, concerns the
ways of PolyP involvement in the regulation of gene expression. While there are appreciable
achievements for bacterial cells in this direction, elucidation of the role of PolyPs in nuclei
is still an important prospective problem for eukaryotes and particularly for the higher
representatives of this kingdom.
At the present time, the significance of PolyP investigations for biochemistry in general
is now clear. In particular, an effective biotechnology approach as a tool for phosphorus
removal from wastewater using polyphosphate-accumulating microorganisms has been de-
veloped (Kortstee et al., 1994; Ohtake et al., 1999; Mino, 2000; Keasling et al., 2000). The
intense attention of researchers has also been drawn to the solution of several important
medical and biological problems associated with polyphosphate biochemistry. First of all,
there is a question about the involvement of PolyPs in the mechanisms of pathogenesis of
a number of pathogenic microorganisms and the creation of novel drugs. In the opinion of
A. Kornberg (1999), one of the targets of novel antimicrobial drugs may be polyphosphate
kinase – an enzyme of PolyP biosynthesis in bacteria. Studies of the participation of PolyPs
and the enzymes of their metabolism in the regulation of bone tissue development also seem
to be promising (Schr¨oder et al., 2000).
Thus, further studies in the field of PolyP biochemistry offer great prospects, which
will more than once give unexpected results for elucidating the most important regulatory
mechanisms of the living cell.